Conical roll mill

ABSTRACT

A conical roll mill apparatus comprised of three or more vertically or horizontally oriented rolls, with the rolls being conically tapered such that the speed of relative movement between mating rolls or a mating roll and the interior surface of the container holding the roll mill is such that the speed will vary along the length of the line of mating contact, whereby said variable speed causes material being mixed or milled between the rolls not only to be caught in the nip contact area by the rolls but also causes a strong shearing effect on the material, and at least one of said rolls being movable axially in order to adjust the amount of clearance which occurs at the nip.

United States Patent Inventor Thomas D. Ough London, England Appl. No 801,589 Filed Feb. 24, 1969 Patented July 6, 1971 Assignee Acheson 1ndustries,1nc.

Port Huron, Mich. Priority Feb. 28, 1968 Great Britain 9717/68 CONICAL ROLL MILL 10 Claims, 6 Drawing Figs.

U.S.C| 241/113, 241/120 Int. Cl B02c 2/00 Field of Search 241/110- [56] References Cited UNITED STATES PATENTS 266,182 10/1882 Montgomery 241/285 X 1,750,088 3/1930 Bragardnmm... 241/109 X 2.574.979 11/1951 Messinger 241/111 Primary Examiner-Robert Cv Riordon Assisran! ExaminerGary L. Smith AltorneyHarness, Dickey & Pierce ABSTRACT: A conical roll mill apparatus comprised of three or more vertically or horizontally oriented rolls, with the rolls being conically tapered such that the speed of relative movement between mating rolls or a mating roll and the interior surface of the container holding the roll mill is such that the speed will vary along the length of the line of mating contact, whereby said variable speed causes material being mixed or milled between the rolls not only to be caught in the nip contact area by the rolls but also causes a strong shearing effect on the material, and at least one of said rolls being movable axially in order to adjust the amount of clearance which occurs at the nip.

CONICAL ROLL MILL BACKGROUND OF THE INVENTION This invention relates to a roll mill for mixing, grinding or dispersing materials.

Many types of apparatus are known for mixing, grinding and dispersing materials, but most suffer from the disadvantage that they cannot handle both thin liquids and very viscous materials. This means that in some processes, for example, when mixing powders with liquids, it is necessary first to premix the materials in one apparatus and then to transfer the paste to another apparatus which is capable of producing a high degree of shear dispersion.

It is an object of the present invention to provide an improved roll mill which can adequately handle many different types of material. Types of material that the roll mill of the present invention is intended to handle include inks, lubricants, foodstuffs, paints, and china clay for papercoating. Some of these materials start in a powder form and have to be thoroughly wetted with very little liquid, mixed in the form of a stiff homogeneous paste until free from lumps, completely dispersed, and then thinnedby mixing with additional liquid.

Other objects, features and advantages of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I illustrates an upright view of a conical roll mill in ac' cordance with this invention being partially shown in cutaway sections;

FIG. 2 illustrates the roll mill as shown in FIG. 1 with the conical rolls withdrawn from the roll mill container pan;

FIG. 3 illustrates a cross-sectional view showing the orientation of the tapered rolls of FIG. 1 and the preferred rotational directions of the rolls and the container pan;

FIG. 4 illustrates an exemplary disposition of a four-roll embodiment of the invention in a generally top plan view;

FIG. 5 illustrates an upright view ofa horizontal roll mill in accordance with this invention, said view being partially in cutaway cross section; and,

FIG. 6 illustrates a top plan view, also in partially cutaway cross section of the roll mill of FIG. 5.

DESCRIPTION OF PREFERRED EMBODIMENTS According to the present invention as shown in FIGS. 1 and 2 there is provided a roll mill designated 10, including a pan 12, the sidewall 12a of which is tapered inwardly towards one end 13 of the pan so that the inside of the sidewall is of frustoconical form, at least three tapered rolls l4, 16, 18 which are rotatable about their axes disposed within the pan 12, a central one 14 of said rolls tapering outwardly towards said one end of the pan and mating with at least two rolls l6 and 18 which taper outwardly towards the other end of the pan, the arrangement of rolls being such that each roll mates either with at least two of the other rolls or with the sidewall of the pan and one other roll, said rolls being mounted on a yoke 30, the yoke and pan being capable of rotation relative to one another about the axis 32 of the pan, and drive means generally designated 34 either for rotating the rolls about their axes whereby the yoke and pan will rotate idly relative to each other or for rotating the pan and yoke relative to each whereby the rolls will idle about their axes.

Because of the tapered form of the pan and rolls, the rolls do not simply roll against each other and against the side of the pan but, for example, with two mating rolls rotating at the same speed, one end of one roll will move faster than the adjacent end ofa mating roll, while the other end of said one roll will move more slowly than the adjacent end of the mating roll. In other words the speed of relative movement between mating rolls or a mating roll and pan will vary along the length of the line of contact. In preferred practice the rollers are rotating in opposite directions which means that the surfaces in contactare going in the same direction.

At one point along each line of contact between mating rolls the rolls will simply roll upon each other but at other points there will be slipping. Thus material being mixed will not only be caught in the nip between mating rolls (or roll and pan) but will be subjected to a strong shearing effect. This means that the roll mill effect can be maintained continuously as distinct from the one pass or feedback arrangement necessary with conventional three-roll mills. Also because of the frequent passing of material between the nips, a quicker shear dispersion effect can be obtained than with the conventional roll mill.

Preferably the central roll 14 is coaxial with the pan 12. The arrangement of the rolls is preferably such that in use, the forces on the rolls are balanced, that is, the outer rolls are equiangularly spaced peripherally around the central roll Thus, if there are only three rolls, two of them are preferably on diametrically opposite sides of the central roll, while if there 'are four rolls three of them are preferably angularly spaced about the central roll by Although there could be more than three (for example seven) rolls mounted on the yoke extending along a diameter of the pan, there is preferably only one roll between the central roll and the sidewall of the pan along any one radius of the pan.

The rolls and pan are described as mating along a line of contact even though they may not actually be in contact. Preferably the spacing (or nip) between the rolls and the pan is adjustable by moving the yoke relative to the pan in a direction parallel to the axis of the pan. Preferably also the arrangement is such that an axial force can be applied between the yoke and the pan so as to apply a force between the rolls and the pan. In some known roll mills, loading of the rolls against the pan i.e. the application of force between roll and pan is achieved by applying a force to the rolls in a direction transverse to its length. With the preferred form of mill of the present invention due to the taper effect of the rolls loading is achieved much more simply.

In addition to axial movement between the yoke and the pan to alter the nip between the rolls and the pan the arrangement is preferably such that the nip between mating rolls can be adjusted. Again this is preferably achieved by arranging for the rolls to be movable relative to one another along their axes of rotation. Either the central roll can be arranged for movement along its axis relative to other rolls, or the outer rolls can be arranged for movement along their axes relative to the central roll. It is possible for each roll to be arranged for movement along its axis relative to the other rolls.

FIG. 3 is a general cross-sectional view taken along the line 3-3 of FIG. 1 showing that in preferred practice the rotation of roll 16 is in a clockwise direction as indicated by the arrow 16a, the rotation of roll 14 is in a counterclockwise direction as indicated by the arrow 14a, and the rotation of roll 18 is in clockwise direction as indicated by the arrow 18a. Also in the usual or preferred practice the pan 12 of FIG. 1 would be rotated in a direction indicated by arrow 12b (FIG. 3), with the movement of the pan being carried out by actuation of the motor 3 and movable base 1 as are more fully described hereinafter.

FIG. 4 illustrates one possible construction in a general cross section plan view, showing how the rolls and pan would be disposed in a four-roll mill apparatus and, FIG. 4 also shows the direction of rotation of the four rolls and pan which could be adopted in the operation of a four-roll-type apparatus.

The mill could be arranged with the axis of the pan and rolls horizontal, as shown in FIGS. 5 and 6, but in preferred arrangement the axis of the pan is vertical with the smaller tapered end closed to form the bottom of the pan.

If the axis of the pan is horizontal the mill can be arranged for continuous operation with an inlet 51 at one end of the pan and an outlet 53 at the other. If the pan is vertical the mill will normally be a batch machine.

Although the drive means may only either rotate the rolls about their axes or produce relative rotation between the yoke and pan, preferably there are drive means which rotate the rolls about their axes and also produce relative rotation between the yoke and pan. Preferably the yoke is fixed and the pan is rotated.

Where the axis of the pan is vertical and the pan is open at its upper and larger end it is preferred to have the yoke movable upwardly so that the rolls can be moved upwardly out of the pan. The yoke can be mounted for vertical movement on two guides on opposite sides of the pan but preferably there is only one support for the yoke on one side of the pan. This arrangement allows uninterrupted access to the pan by permitting the yoke to be swung clear in a horizontal direction.

The angle of taper of the rolls and of the pan can be chosen to suit the particular purposes for which the mill is intended. For example the angle of inclination of the surface of the rolls and of the pan to their axes may be within the range from about l2 to about 18.

The speed of rotation of the pan and rolls may also be chosen to suit the material to be mixed.

The materials from which the rolls and pan are formed are also chosen depending on the type of material to be mixed. The roll surface can be highly polished, roughened or even fluted.

The rolls and/or the pan may be provided with a jacket or system for supplying a heating or cooling medium.

In order that the invention may be well understood two preferred embodiments will now be further described in detail by way of example.

The roll mill for mixing, grinding or dispersing batches of materials includes a base 1 which supports pan 12. The pan has the sidewall 120 the inner surface of which tapers outwardly from the closed bottom 13 upwards, so that is is of frustoconical form. The pan 12 is held on a turntable l which is rotatable by a motor 3 within the base, so that the pan can be rotated about its axis. An exemplary pan has an internal depth of about 12 inches and has a top internal diameter of 24 inches.

Extending upwardly from the base 1 to one side of the pan there are vertical pillars 7 which support yoke 30 which extends horizontally over the pan. The yoke has three bearings 31 for shafts 33 for rolls which extend downwardly into the pan. The vertical pillar designated 9 can be extended an retracted hydraulically by the drive means H so that the rolls can be removed from, and returned into, the pan.

The rolls are tapered, and the central roll which is coaxial with the pan tapers outwardly towards its bottom end. The other two rolls mate with the central roll and also with the sidewall of the pan. These two outer rolls therefore taper inwardly towards their bottom end.

When disposed within the pan the centers of the three rolls l4, 16, 18 lie on a diameter of the pan 12.

The shafts 33 of the three rolls each carry a similar spur gear 41, each of which meshes with its adjacent spur gear, and the shaft nearest the pillar is driven at 43 so that all these shafts rotate at the same speed. The motor 45 for driving the rolls is housed on the pillar.

The hydraulic means for raising and lowering the yoke includes stop means (not shown) adjustable by a micrometer to control the extent to which the yoke 30 is lowered. Adjustment of this stop will therefore determine the nip between the outer rolls and the pan. ln addition the shafts 33 of the two outer rolls 16, 18 can be moved along their axes and adjusted by a micrometer, and such adjustment will determine the nip between the outer rolls and the central roll. Scrapers may be provided at the top of the pan to return material into the pan that has risen up the sidewalls of the pan. Scrapers may also be provided for directing material into the nip between the rolls, and between the rolls and the side of the pan.

In use, due to the rotation of the rolls, material is squeezed through the nip between the rolls or between the rolls and the pan. Since the rolls are tapered there is a differential speed of relative movement along the length of the rolls so that material is subjected to heavy shearing. This can be controlled by altering the nip between the rolls and the speed of rotation of the rolls. Since the pan rotates relative to the rolls, the material that has passed between two rolls or between the rolls and pan is returned and brought into a position where it will again be passed between two rolls. The high degree of differential velocity obtained and the frequent passes that the material is obliged to make between the rolls or between rolls and pan ensures very quick and efficient shear dispersion.

FIGS. 5 and 6 illustrate a roll mill 10a differing from the roll mill [0 described above in that the axis of the pan 12a is horizontal instead of vertical, so that the mill can be operated continuously. The pan 12a is not closed at both ends, but instead is effectively a frustoconical sleeve which is mounted for rotation in ring bearings 101 at both ends. Three tapered rolls 14a, 16a, 18a with their axes horizontal are disposed within the pan and have shafts projecting from both ends which are mounted in the bearings 101 at both ends of the pan. The axes of the three shafts lie in a horizontal plane. The shafts and the pan are driven by a motor 103 via gears and the cooperation of the rolls with each other and with the pan is similar to the batch roll mill 10 described above.

Fixed plates 105 and 107 which do not rotate with the pan 12a close the pan at both ends. One chute 51 extends through a hole in the top of the plate 107 at the smaller end of the pan for introducing material into the pan, and another chute 53 extends out of a hole at the bottom of the plate 105 at the larger end of the pan, for discharge of material out of the pan. By introducing a constant flow of material through the charging chute, mixed material will be discharged continuously and the mill will operate continuously.

.What i claim is:

1. A conical roll mill apparatus, for milling various materials, comprising,

at least three conically tapered rolls,

drive means for rotating at least one of the rolls,

at least two different nip areas formed between the rolls,

container means within which the rolls are positioned to carry out the milling operation,

tapered interior surface means, on the container means, for providing a nip area between at least one of the rolls and the surface means,

means for supporting said container means,

and, means operative to rotate said container means.

2. A conical roll mill apparatus, for milling various materials, comprising,

at least three conically tapered rolls,

drive means for rotating at least one of the rolls,

at least two different nip areas formed between the rolls,

container means within which the rolls are positioned to carry out the milling operation,

tapered interior surface means, on the container means, for providing a nip area between at least one of the rolls and the surface means,

means for supporting said container means,

and, drive means for removing and inserting the. rolls into the container means.

3. A conical roll mill apparatus, for milling various materials, comprising,

at least three conically tapered rolls,

drive means for rotating at least one of the rolls,

at least two different nip areas formed between the rolls,

container means within which the rolls are positioned to carry out the milling operation,

tapered interior surface means, on the container means, for providing a nip area between at least one of the rolls and the surface means,

means for supporting said container means,

means operative to rotate said container means, and

7. The apparatus of claim 2 further characterized in that the axes of rotation of said rolls are oriented in a generally vertical disposition.

8. The apparatus ofclaim 2 further characterized in that the axes of rotation of said rolls are oriented in a generally horizontal disposition.

9. The apparatus of claim 3 further characterized in that the axes of rotation of said rolls are oriented in a generally vertical disposition.

10. The apparatus of claim 3 further characterized in that the axes of rotation of said rolls are oriented in a generally horizontal disposition. 

1. A conical roll mill apparatus, for milling various materials, comprising, at least three conically tapered rolls, drive means for rotating at least one of the rolls, at least two different nip areas formed between the rolls, container means within which the rolls are positioned to carry out the milling operation, tapered interior surface means, on the container means, for providing a nip area between at least one of the rolls and the surface means, means for supporting said container means, and, means operative to rotate said container means.
 2. A conical roll mill apparatus, for milling various materials, comprising, at least three conically tapered rolls, drive means for rotating at least one of the rolls, at least two different nip areas formed between the rolls, container means within which the rolls are positioned to carry out the milling operation, tapered interior surface means, on the container means, for providing a nip area between at least one of the rolls and the surface means, means for supporting said container means, and, drive means for removing and inserting the rolls into the container means.
 3. A conical roll mill apparatus, for milling various materials, comprising, at least three conically tapered rolls, drive means for rotating at least one of the rolls, at least two different nip areas formed between the rolls, container means within which the rolls are positioned to carry out the milling operation, tapered interior surface means, on the container means, for providing a nip area between at least one of the rolls and the surface means, means for supporting said container means, means operative to rotate said container means, and drive means for remaining and inserting rolls into the container means.
 4. The apparatus of claim 1 further characterized in that, the axes of rotation of said rolls are oriented in a generally vertical disposition.
 5. The apparatus of claim 1 further characterized in that, the axes of rotation of said rolls are oriented in a generally horizontal disposition.
 6. The apparatus of claim 5 further characterized as including, means for continuously operating said apparatus and operative to continuously introduce and remove said various materials to the milling operation.
 7. The apparatus of claim 2 further characterized in that the axes of rotation of said rolls are oriented in a generally vertical disposition.
 8. The apparatus of claim 2 further characterized in that the axes of rotation of said rolls are oriented in a generally horizontal disposition.
 9. The apparatus of claim 3 further characterized in that the axes of rotation of said rolls are oriented in a generally vertical disposition.
 10. The apparatus of claim 3 further characterized in that the axes of rotation of said rolls are oriented in a generally horizontal disposition. 